Moisture-related flooring failures cost over $2.4 billion every year. But your business doesn’t have to be part of that stat. As a flooring professional, your solution is simple: You can measure moisture deep inside concrete subfloors using in-situ relative humidity (RH) testing. It’s the gold standard for taking accurate concrete moisture readings. And it helps you decide when to install floor coverings so you can cut way down on callbacks and costly repairs.
But first, the type of moisture testing you use makes such a big difference. Some moisture in concrete flooring is normal, but excess moisture can cause floor covering damage such as buckling, bubbling and adhesive breakdown. Here’s why: Concrete starts as a mix of cement, water and aggregate like sand and gravel. This combination causes curing—the chemical hardening process that turns the mixture into concrete.
Concrete will slowly release any water not needed for curing and hardening. But even after it’s “dry,” it can still absorb and release moisture through its pores. Concrete never dries completely, but in the proper environment, it eventually releases enough moisture for flooring installation. Concrete subfloors usually get poured over a moisture retarder—and that’s a good thing. But it means any excess moisture in the slab evaporates through the surface during the concrete drying process.
That’s why it’s vital to take accurate concrete moisture readings before making a final flooring installation decision. Install floor covering too soon, and you could damage anything you install over the slab.
Why deep moisture testing matters
Concrete slabs dry faster on the surface. A slab that’s open to the surface on one side holds more moisture in the bottom half. And a slab that’s open on two sides holds more moisture in the middle. For a true picture of slab moisture, you need to test at a depth of 40% of its thickness (or 20% for slab drying on two sides). This gives you an accurate idea of when you can install floor coverings without risking damage to adhesives, finishes and other flooring materials.
Concrete moisture meters only measure around the top ½-inch of concrete and give you readings on a relative scale. RH testing with in-situ probes, however, can measure RH in concrete at the 40% depth needed for accurate moisture readings. And it can actually quantify the amount of moisture that still needs to work its way out.
But both tests have their place. In fact—they make a great team. You can start with a concrete moisture meter for surface moisture testing: First, take instant measurements to spot check for the wettest areas of concrete. Next, use the readings to decide where to do further moisture testing. This meets the ASTM F2659 procedure for taking preliminary moisture readings in concrete.
Follow up with RH testing for deep moisture testing. Use the readings from the moisture meter to place in-situ testing probes at 40% (or 20%) depth. Wait 24 hours after probe placement to take readings. Take a reading from each probe; you can use this info to make a final flooring decision, per ASTM F2170 procedure.
Before you install flooring, concrete needs to reach an RH of 75% or below—or whatever the flooring manufacturer specifies. You’ll want to keep a record of your final RH readings to protect the flooring warranty.
Jason Spangler, Wagner Meters’ sales manager, has more than 25 years’ experience in sales and sales management across a broad spectrum of industries. For more information, call 855.350.7719.
